Add platforms.h header to determine platform

The platforms.h header will allow for using/implementing OS-specific
code that will differ based on the platform the program is compiled for.

cosmopolitan/Makefile

@@ -14,7 +14,8 @@ HEADERS = \
 		../src/parser.h \
 		../src/algorithms/linear_congruential_gen.h \
 		../src/data_structures/linked_list.h \
-		../src/data_structures/hash_map.h
+		../src/data_structures/hash_map.h \
+		../src/platforms.h
 
 OBJECTS = $(addprefix ${OBJDIR}/,$(subst ..,PREVDIR,$(patsubst %.c,%.c.o,${SOURCES})))
 

src/platforms.h

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2024 Stephen Seo
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * `platforms.h` is the header that determines what platform this program is
+ * compiled for.
+ */
+
+// Determine platform macros
+#define SIMPLE_ARCHIVER_PLATFORM_WINDOWS 1
+#define SIMPLE_ARCHIVER_PLATFORM_MAC 2
+#define SIMPLE_ARCHIVER_PLATFORM_LINUX 3
+#define SIMPLE_ARCHIVER_PLATFORM_COSMOPOLITAN 4
+#define SIMPLE_ARCHIVER_PLATFORM_UNKNOWN 0
+
+#if defined __COSMOPOLITAN__
+# define SIMPLE_ARCHIVER_PLATFORM SIMPLE_ARCHIVER_PLATFORM_COSMOPOLITAN
+#elif defined _WIN32
+# define SIMPLE_ARCHIVER_PLATFORM SIMPLE_ARCHIVER_PLATFORM_WINDOWS
+#elif defined __APPLE__
+# define SIMPLE_ARCHIVER_PLATFORM SIMPLE_ARCHIVER_PLATFORM_MAC
+#elif defined __linux__
+# define SIMPLE_ARCHIVER_PLATFORM SIMPLE_ARCHIVER_PLATFORM_LINUX
+#else
+# define SIMPLE_ARCHIVER_PLATFORM SIMPLE_ARCHIVER_PLATFORM_UNKNOWN
+#endif